(80a) Production of High-Purity Pyrene Oligomers in a Supercritical Fluids Medium

Polycyclic aromatic hydrocarbons (PAHs) have been shown to be ideal precursors for liquid crystalline materials, due to their ability to form an ordered mesophase. This feature gives them excellent heat and charge­-transfer properties, which are needed for many applications. In our group, we have focused our work on the PAH pyrene. In that work, pyrene was catalytically reacted to form pyrene oligomers, which were then fractionated for individual property testing. During that testing, we found that the pyrene trimer oligomer was able to form 100% mesophase, making it the lowest melting point mesophase ever discovered.

Unfortunately, the current method of reacting pyrene monomer to form trimer results in trimer yields that are fairly low; thus, the oligomeric product must be extracted and purified, which is time-consuming, expensive, and difficult to scale up. Thus, we are interested in methods in which the pyrene reaction will be cut off at the desired oligomer, resulting in a higher-purity oligomeric product.

Using our knowledge of the solubility of pyrene oligomers in supercritical (SC) toluene, we are reacting a pure pyrene with AlCl₃ catalyst in the presence of SC toluene. At appropriate temperatures and pressures, the SC toluene solubilizes the monomer and any dimer products from the reaction, while any trimer produced will precipitate out of solution because of its low solubility. Once precipitated from solution, the trimer reacts far less with the monomer and dimer reactants, meaning that the monomer and dimer will continue to react only with themselves. This process can be carried out until the final mixture is left with a much higher concentration of trimer. Preliminary results indicate that trimer concentrations can be at least doubled when pyrene oligomerization is carried out in the presence of supercritical toluene.